The present invention relates to a method for preparing phosphoramides substantially free of acidic, basic, or halide impurities, or their precursors. The invention also relates to resin compositions comprising at least one thermoplastic resin and at least one phosphoramide having a glass transition temperature of at least about 0xc2x0 C., wherein the phosphoramide is prepared by the method of the invention.
Compounds containing phosphorus have been used in resin compositions for a variety of reasons. For example, various phosphites have been utilized to enhance the melt stability and/or color stability of resin compositions. Alternatively, various organic phosphate esters have been utilized in resin compositions to improve the flame resistance properties of the compositions and/or to enhance the melt flow characteristics of the compositions. Certain water soluble phosphoramides have also been used in the textile industry as flame retardant finishes for fabrics.
As part consolidation and weight reduction continues to evolve in many industries, the physical property demands placed upon resin manufacturers are increasing. Key industries increasing the demands include the electronics and computer industries, especially for computer housings, computer monitor housings, and printer housings. One increasing demand is for materials that possess higher heat resistance while substantially retaining other key physical properties. Another increasing demand is for materials that are rated in the Underwriter""s Laboratory UL-94 test protocol as V-0, V-1, or V-2.
Resinous compositions containing phosphoramides are known which meet many of these property requirements. However, acidic, basic, or halide species, or their precursors present as impurities in phosphoramides often result in deleterious effects on resin composition properties such as molecular weight loss in one or more resinous components. There is a need for phosphoramides substantially free of acidic, basic, or halide impurities (or their precursors) for use in preparing new resin compositions that meet stringent property requirements such as flame retardancy, heat resistance, and hydrolysis resistance
In one embodiment the present invention is a method for preparing a sterically hindered phosphoramide having a glass transition temperature in one embodiment of at least about 0xc2x0 C., which comprises contacting a sterically hindered diaryl chlorophosphate with a basic nitrogen compound containing at least two basic Nxe2x80x94H groups, wherein the reaction is conducted with substantial elimination of water such that less than about 2 wt. % of pyrophosphate is formed based on the weight of phosphoramide. In another embodiment the present invention is directed to a resin composition comprising the following and any reaction products thereof: a) at least one thermoplastic resin, and b) at least one phosphoramide having a glass transition point of at least about 0xc2x0 C., wherein the phosphoramide is made by the method which comprises contacting a sterically hindered diaryl chlorophosphate with a basic nitrogen compound containing at least two basic Nxe2x80x94H groups, wherein the reaction is conducted with substantial elimination of water such that less than about 2 wt. % of pyrophosphate is formed based on the weight of phosphoramide. Various other features, aspects, and advantages of the present invention will become more apparent with reference to the following description and appended claims.